Docker‑Based Dual‑Ubuntu Network Namespace Demo

This project simulates two Ubuntu “VMs” (ubuntu1 and ubuntu2) connected by a Docker bridge. Each container creates two Linux network namespaces (NS1, NS2), attaches them to an internal bridge (br0), and then routes between the namespaces of both containers.

Prerequisites

• Docker installed and running (tested on Docker Engine ≥ 20.10).
• Basic familiarity with docker run, docker exec, and Linux networking (ip, ip netns, bridge).
• Host machine able to allocate 192.168.0.0/24 for Docker (no conflicts).

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Steps

1. Create a folder (e.g. netns-demo/) and save the following Dockerfile as Dockerfile:

   FROM ubuntu:latest
   
   ENV DEBIAN_FRONTEND=noninteractive
   
   RUN apt-get update && apt-get install -y --no-install-recommends \
       curl \
       wget \
       iputils-ping \
       iptables \
       net-tools \
       iproute2 \
       vim \
       less \
       ca-certificates \
       gnupg \
       && rm -rf /var/lib/apt/lists/*
   
   CMD [ "bash" ]

2. From that folder, build the image

   docker build -t ubuntu-with-utils .

3. Create a Docker Bridge Network We need a user-defined bridge so we can assign static IPs (192.168.0.10 and 192.168.0.11) to our two containers. On the host, run:

   docker network create \
   --driver=bridge \
   --subnet=192.168.0.0/24 \
   my-bridge-net

4. Launch the Two Ubuntu Containers

   # Run ubuntu1
   docker run -it \
   --name ubuntu1 \
   --privileged \
   --network my-bridge-net \
   --ip 192.168.0.10 \
   ubuntu-with-utils \
   bash
   
   # In new terminal, run ubuntu2 
   docker run -it \
   --name ubuntu2 \
   --privileged \
   --network my-bridge-net \
   --ip 192.168.0.11 \
   ubuntu-with-utils \
   bash

5. Copy & Run the Setup Scripts There are two separate scripts: one for ubuntu1 (container IP 192.168.0.10) and one for ubuntu2 (container IP 192.168.0.11). Each script:

   • Creates two network namespaces (NS1, NS2).
   • Builds a Linux bridge (br0) and two veth pairs connecting those namespaces.
   • Assigns IP addresses and brings up all interfaces.
   • Enables IPv4 forwarding + sets iptables to ACCEPT FORWARD.
   • Installs a host‐level route that points to the other container’s Docker IP.

   Now, copy setup-ubuntu1.sh and run it inside ubuntu1. Next, copy setup-ubuntu2.sh and run it inside ubuntu2.

6. Test and Verify Connectivity Once both scripts have completed successfully, you can test all the links from inside ubuntu1. If all pings succeed, your dual-container, multi-namespace network is fully operational.

7. Cleanup When you’re done and want to tear everything down, from your host run:

   docker rm -f ubuntu1 ubuntu2
   docker network rm my-bridge-net